Water-base lubricant composition



United States Patent Office 3,007,871 Patented Nov. 7, 1961 3,007,871WATER-BASE LUBRICANT COMPOSITION Robert P. Pardee, Albuquerque, N. Mex.,and Joseph F. Lyons, Poughkeepsie, N.Y., assignors to Texaco Inc., acorporation of Delaware No Drawing. Filed Apr. 8, 1958, Ser. No. 727,05510 Claims. (Cl. ESL-46.4)

This invention relates to an improved Water-base lubri- \cantcomposition. More particularly, the invention relates to an improvedwater-base cutting fluid.

Cutting fluids essentially function both as coolants and lubricants inmachining of metals. As a coolant, the fluid acts to cool the cuttingtool so as to reduce abrasive wear and loss of hardness, and to cool theWork to prevent distortion and dimensional inaccuracies. As a lubricant,the fluid acts to lubricate the chip-tool interface to reduce frictionalheat, tool wear, and power consumption, and to improve surface finish.The fluid in its lubricating capacity also acts to prevent welding ofmetal to tool point and subsequent rough surfaces due to slough in-g-offof the built-up edge on the finished face of the work.

Cutting fluids also play secondary but nevertheless important roles inmachining operations. The fluid should flush chips away from the workarea; protect the finished work surfaces, the tools, and the machinesagainst rust and discoloration; be smokeless and fogless in use; andeither be odorless or have reasonably pleasant odor.

Generally, Water is one of the best coolants known and also performs thesecondary roles of cutting fluids in an excellent manner. However waterlacks essential lubricating characteristics necessary for a good cuttingfluid. 'For example water lacks the film strength inherent in goodmineral oils. This is essential to the cutting fluid in order to formand maintain a tough lubricant film to reduce friction between the tooland the work to protect the surface from being married by bits ofabrasive materials which may be present.

In accordance with the present invention a composition which meets therequirements of a good cutting fluid and includes superior cooling andlubricating properties comprises a major portion of Water and a minoramount of the combination of a water soluble metal phosphate and a watersoluble metal thiocyanate suflicient to improve the extreme pressureproperty of the composition. The amounts of each of these salts foundeffective in the combination ranges from 0.1 to about 5 percent byweight. The preferred combination is about 2.0 percent phosphate and 2.0percent thiocyanate in a water base to obtain an excellent cuttingfluid. The combination may vary in the amount and ratio of theconstituents. For example 1.0 percent phosphate and 0.5 percentthiocyanate, or 0.5 percent phosphate and 3.0 percent thiocyanate.

The preferred metals used in the salts are the alkali metals includingpotassium, sodium and lithium. Other metals which form water solublephosphate and thiocyanate salts are also very useful for the combniationof the invention. The alkaline earth metals are excellent metalcomponents for the salts. The phosphate of copper, and the thiocyanatesof copper; zinc, manganese and iron are examples of other Water solublesalts which are useful for the present invention. The metal portion ofthe phosphate and thiocyanate molecules can be the same or different inthe combination of the invention however the metal is usually the samein each salt.

A rust inhibitor, such as a nitrite salt or an amine, is generallyemployed in the composition of the invention. Triethanolamine ispreferred and in amounts ranging from 0.1 to l percen Other additives,such as water soluble extreme pressure agents, sequestering or settlingagents, detergents, dyes an bactericides can be added to the compositionwithout any deleterious effect.

This invention also includes an improvement in an orthogonal metalcutting process wherein a tool is directed against the metal to removechips. The improvement comprises contacting the cutting edge of the tooland the work surface of the metal with water containing a minor amountof a water soluble metal thioeyanate suflicient to lend lubricity to thewater. The minor amounts found useful range from about 0.5 to 5 percentby weight. The alkali metals are particularly good for the thiocyanatesalt of the invention but alkaline earth metals, copper, Zinc, manganeseand iron thiocyanates are also excellent in the process.

Other additives including rust-inhibitors such as nitrites or amines,are generally employed in the water-base composition of the process.

To demonstrate the excellence of the compositions of the invention withrespect to extreme pressure property they were subjected to the wellknown Mean Hertz Load Test a description of which is set forth in US.Patent 2,600,058. Briefly, the test consists of rotating a steel ballunder pressure against three locked steel balls.

' The test lubricant is applied to the balls and the amount of wearoccurring at the rubbing points is a measure of the extreme pressureproperty of the lubricant tested. The more pressure which can be exertedwithout increasing the amount of wear, the better the extreme pressureproperty of the lubricant.

The following table shows the Hertz Load Test:

results of the Mean As a further means of determining the extremepressure property or wear resistance of the compositions of theinvention, they were subjected to the SAE Load Test (500 rpm.) thefollowing table shows the results of this testing.

TABLE II SAE (500 Run Distilled Water Plus Additive rpm.)

Avg. Scale Load, lbs

N o additive 92 2% K PO4+0.5% triethanolarninc 82 2% KCNS+0.5%triethanolamine 206 4% K3PO4+0.5% trietl1anolamine 144 4% KCNS+0.5%triethanolamine 433 2% KONS+2% K PO4+0.5% trietha- 550+ nolamine.

In Tables I and II the unexpectedly high extreme pressure property ofcompositions of the invention is well demonstrated. This feature ofsupplying better lubrieating properties to water is not new but theexcellence of compositions of the invention in this respect was notexpected.

The water-base compositions containing just the chiccyanate although notas good as those containing the combination phosphate and thiocyanatenevertheless show unexpectedly good results in these extreme pressurebench tests as compared to the fluids containing just the phosphate.

The compositions are suitable for hydraulic systems or other systems aswell as for cutting fluids where extreme pressure or anti-wearproperties are desired. Such lubricant compositions are superior tomineral oil or oil emulsions since they are non-combustible and stablein storage.

As previously stated, the compositions of the invention are particularlysuitable as cutting fluids owing to the excellent cooling propertyafforded by the presence of large amounts of water as well as theimproved lubricating properties. The efliciency of cutting fluids is nowwell able to be determined by a test procedure disclosed in copendingco-assigned application of Norwin C. Derby, S.N. 719,193 filed March 5,1958. This test procedure briefly consists of measuring the electricalresistance of a metal chip produced from a cut of known length in ametal turning operation wherein a cutting fluid, the efficiency of whichis to be measured, is employed. This resistance measurement is comparedto the electrical resistance of a chip formed from a cut of a lengthequal to the cut from which the other chip was formed while utilizing acutting fluid having a known efficiency. The higher the electricalresistance, the more efficient is the cutting fluid.

The specific test procedure is as follows:

Details of apparatus The lathe employed for this test was an AmericanPacemaker, a 16 inch by 30 inch tool room metal cutting lathe.

The test tool was a Rex AA high speed steel blank measuring /8 inch by76 inch by 3 inches in length and supplied by Crucible Steel Co. Thetool blank met the following specifications:

Tungsten "percent" 18.00 Chromium do 4.00 Vanadium do 1.10 Carbon do0.73 Hardness, Rockwell C-63 The cutting head of the tool was of an inchin length. The side vertical face of the cutting head, forming one facetof the cutting edge, was a minimum of 5 of an inch in height and wasground at a 4 angle starting from the cutting edge. The top horizontalface of the cutting head, which formed the other facet of the cuttingedge, was ground at an 8 angle starting from the cutting edge. The endvertical face of the cutting head was ground at a 4 angle starting fromthe top horizontal edge and at a 4 angle starting from the frontvertical edge of the cutting head. This vertical edge was initiallyrounded to a radius of 0.010 of an inch. The three ground faces of thetool had a maximum surface roughness of two (2) microinchcsroot-mean-square as measured with a Brush Surface Analyzer.

The metal stock or billet to be cut in the lathe was vanadium deoxidizedsteel, stock C-45, furnished by the Bethlehem Steel Co. The billet was88 /2 inches in diameter as received but was reduced to 7 /2 inches fortesting. The ladle analysis of the steel used for this billet was asfollows:

Carbon percent 0.48 Manganese do 0.89 Phosphorous do 0.010 Sulfur do0.027 Silicon do 0.25 Vanadium do 0.16 Tensile strength lbs./ sq. in.--87,000 Yield point lbs./sq. in 50,000 Brinell hardness 163-174 Detailsof procedure As previously indicated, the billet was slotted or scoredlongitudinally to a depth of about one-fourth the depth of the intendedtest cutting depth. A scoring tool made from the same type blankpreviously described and having a cutting head ground down to A3 inch inlength, A inch in height and inch in width was used. The cutting edgewas along the A inch width and the front face was ground at an 8 anglestarting from the cutting edge.

This slotting tool was mounted in the tool post of the lathe with itscenter line in the same horizontal plane as the centerline of the billetbut perpendicular thereto. The slotting tool was oriented with thecutting edge tangential to the cylindrical billet. With the billetlocked, the cutting tool was traversed longitudinally along the billetusing the hand travel crank of the lathe apron. A number of passes weremade taking only a few thousandths of an inch on each pass until a depthof A of an inch was reached.

After slotting the billet, the slotting tool was removed and the testcutting tool was mounted in the tool post with the cutting edge of thetool at the center line of the billet perpendicular to and with the endof the tool 0.150 of an inch beyond the face of the billet at thestarting end thereof. The lathe feed was adjusted to give a feed of0.002 of an inch per revolution of the billet. Therefore, for eachrevolution a volume of metal 0.002 of an inch thick, 0.150 of an inchwide and equal in length to the circumference of the billet was removed.

The cutting speed of the lathe was set at 180 surface feet per minuteand the cutting oil flow was at the rate of 4 gallons per minute.

With a freshly ground tool a ten second cut was made under the aboveconditions and the chips thrown away. Then, another ten second cut wasmade for the test. This cut was terminated by stopping the lathe leavingthe chip attached to the billet. The chip was broken off and starting atthat end the chip was examined until the first crack caused by the slotwas found. The end portion was removed and the next ten segmentsdesignated by the cracks spaced along the chip were saved for resistancemeasurement.

The ten segments were separated into individual chips and then washed inStoddard solvent and etched in oxalic acid to assure good electricalcontact. Their electrical resistance was then measured on a standardWheatstone Bridge Modified only by the addition of small clamps tocontact and hold the end of the chips.

Two more ten second cuts as described above were made using the sametool. The same procedure, of four ten second cuts, was then followed foreach of two other new cutting tools. This resulted in a total of ninetychips which were measured for electrical resistance. These ninetyelectrical resistance measurements were subsequently averaged to obtainthe rating of the cutting oil for the run.

The results of this Chip Resistance Test on certain fluids including thecomposition of the invention is set forth in the following table.

TABLE III Chip Resist- Distilled Water Plus Additive ance (milliohms) Noadditive 65 4% Reference Fluid 1 76 2% K3PO4+0.5% triethan01amine 84 2%KCNS+0.5% triethanolamine 98 2% K3PO4+2% KCNS+0.5% triethanolatuin Ihereference fluid consisted of 20% (wt) polyethylene glycol (M.W.=600), 9%(wt) sodium nitrite, 7% (wt) triethanolamine, and 25 ppm. brilliant bluedye.

We claim:

1. A lubricant composition comprising a major proportion of water, andthe synergistic combination of from 0.1 to 5 percent by weight of atri-alkali metal ortho phosphate and from 0.1 to 5 percent of an alkalimetal thiocyanate, in sufiicient amounts to impart substantiallyimproved extreme pressure properties to the said composit-ion.

2. A lubricant composition comprising a major proportion of water, thesynergistic combination of from 0.1 to 5 percent by weight of atri-alkali metal ortho phosphate and 0.1 to 5 percent of an alkali metalthiocyanate in sufiicient amounts to impart substantially improvedextreme pressure properties to the said composition, and a rninorproportion of an alkylolarnine having rust inhibiting properties.

3. A lubricant composition comprising a major proportion of water, thesynergistic combination of from 1 to 3 percent by weight oftri-potassium ortho phosphate and from 1 to 3 percent potassiumthiocyanate, and from 0.1 to 1 percent by weight of thieth-anolamine.

4. In an orthogonal metal cutting process wherein a tool is directedagainst the metal to remove chips, the improvement which comprisescontacting the cutting edge of the tool and the work surface of themetal during the cutting operation with water containing a minor amountof a water soluble metal thiocyanate sufficient to impart improvedextreme pressure properties to the water.

5. In an orthogonal metal cutting process wherein a tool is directedagainst the metal to remove chips, the improvement which comprisescontacting the cutting edge of the tool and the work surface of themetal during the cutting operation with water containing from about 0.5to 5 percent by weight of an alkali metal thiocyanate, said thiocyanatebeing present in a sufiicient amount to impart extreme pressureproperties to the water.

6. The orthogonal metal cutting process as described in claim 5 whereina minor proportion of an alkylolamine having rust inhibiting propertiesis included in the water.

7. The orthogonal metal cutting process as described in claim 6 whereinthe said alkylolamine is triethanolamine in the amount of 0.1 to 1percent by weight.

8. In an orthogonal metal cutting process wherein a tool is directedagainst the metal to remove chips, the improvement which comprisescontacting the cutting edge of the tool and the work surface of themetal during the cutting operation with water containing about 0.5-5percent by weight of a water soluble tri-alkali metal ortho phosphateand about 0.5-5 percent by Weight of an alkali metal thiocyanatesufficient to impart improved extreme pressure properties to the water.

9. The orthogonal metal cutting process as described in claim 8 whereinthe water contains a minor proportion of an alkylolarnine having rustinhibiting properties.

10. The orthogonal metal cutting process as described in claim 9 whereinthe water contains the combination of from 1 to 3 percent by weight oftri-potassium ortho phosphate and from 1 to 3 percent potassiumthiocyanate, and from 0.1 to 1 percent by weight of triethanolamine.

References Cited in the file of this patent UNITED STATES PATENTS2,008,939 Tufts July 23, 1935 2,198,965 Hochwalt Mar. 19, 1940 2,318,629Prutton May 11, 1943 2,432,784 Miller Dec. 16, 1947 2,474,325 RodgersJune 28, 1949 2,825,693 Beaubien et a1 Mar. 4, 1958 UNITED STATES PATENTOFFICE CERTIFICATION OF CORRECTION Patent No, 3 007 871 November 7 1961Robert P. Pardee et a1,

It is hereby certified that error appears in the above numbered patentrequiring correction and th at the said Letters Patent should read ascorrected below.

Column 1 line 38 for "married" read marred V column 5 line 21 for"thiethanolamine" read triethanolamine Signed and sealed this 10th dayof April 1962,

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents

1. A LUBRICANT COMPOSITION COMPRISING A MAJOR PROPORTION OF WATER, ANDTHE SYNERGISTIC COMBINATION OF FROM 0.1 TO 5 PERCENT BY WEIGHT OF ATRI-ALKALI METAL ORTHO PHOSPHATE AND FROM 0.1 TO 5 PERCENT OF AN ALKALIMETAL THIOCYANATE, IN SUFFICIENT AMOUNTS TO IMPART SUBSTANTIALLYIMPROVED EXTREME PRESSURE PROPERTIES TO THE SAID COMPOSITION.